Scruffy is right, you need .Net Framework 3.5 for this to work properly on XP. Vista usually comes with it.
Latest Weapon Modifier (SFCO) Version: 9.0 OpenSource Download
Latest Weapon Modifier (SFLS) Version: 1.0 Beta Download
Tutorials
NitePR Guide by WhoIsYou
+Reputation if you like my work =] Thanks!